The invention relates to a medical catheter instrument comprising a shaft portion, a distal portion that can be bent in a controlled manner in at least one direction relative to the shaft portion, and at least one control element that extends in an axially moveable manner through the shaft portion to the distal portion; and that the axial movement of the control element controls a corresponding bending movement of the distal portion.
Medical catheter instruments of this kind are known in various designs. Thus, the patent specification U.S. Pat. No. 7,033,345 B2 discloses a catheter instrument with a control element that is formed by a tension wire, which extends from a grip region of the catheter through the shaft portion and the distal portion inside an associated tension wire lumen as far as the front end of the distal portion, where said tension wire is fastened. A more or less central hollow channel serves as the working channel. In an additional lumen the distal portion has a rubber element with a rectangular cross section. This rubber element acts as the stiffening element, which is supposed to bring about the resetting of the distal portion into its linear starting position from its bent position, when the restoring movement is released by relaxing the tension wire.
The patent specification EP 0 489 937 B1 discloses a medical catheter instrument with two tension cable pieces, which serve as the control element for controlling an active bending movement of the distal portion in a plane of the bending movement. These two pieces of the tension cables are arranged opposite each other with respect to a longitudinally central working/hollow channel of the catheter. In this case the tension wires run directly in a respective lumen of solid material inside the distal portion, whereas inside the shaft portion the tension wires run in a sleeve that increases the flexural rigidity and that in turn is inserted into a corresponding lumen of solid material. In the plane that extends perpendicular to the plane of the bending movement, strips having a rectangular cross section are incorporated into the distal portion. Said strips are supposed to stabilize the distal portion and to counteract the said distal portion's deflections transversely to the plane of the bending movement. The tension cable pieces are implemented as sections of a common continuous tension cable comprising a connecting piece that is fastened at a front end cap of the distal portion.
The patent specification DE 103 37 580 B4 discloses a catheter that is provided with a control element that is designed to transmit both pull and push forces, so that the result is a deflectability of the distal portion of the catheter in two opposite directions with the use of only this one control element.
Additional medical catheter instruments of the type mentioned in the introductory part are disclosed in the Offenlegungsschrift [published patent application] WO 97/01369 A1 and WO 95/31243 A1.
The engineering object of the present invention is to provide a medical catheter instrument of the type mentioned in the introductory part that enables a deflectability of the distal portion with a high degree of functional reliability, a high degree of flexibility when in use and/or at a comparatively low production cost.
The invention achieves this object by providing a medical catheter instrument comprising a shaft portion, a distal portion that can be bent in a controlled manner in at least one direction relative to the shaft portion, and at least one control element that extends in an axially moveable manner through the shaft portion to the distal portion. The axial movement of the control element controls a corresponding bending movement of the distal portion. At least one bending assembly comprises at least one elongated, elastically flexible stiffening element and at least one elongated, flexible and axially length-variable bending element. The stiffening element and the bending element are both provided in at least one axial subregion of the distal portion and extend therein with an axial main component, wherein the stiffening element forms a bending movement restoring element, which has a higher flexural rigidity than the at least one bending element. The bending element is coupled to the at least one control element or forms a part of the control element.
This catheter instrument contains one or more bending assemblies that comprise at least one elongated, elastically flexible stiffening element and at least one elongated, flexible and axially length-variable bending element. The stiffening element and the bending element are both provided in at least one axial subregion of the distal portion and extend therein with an axial main component—that is, totally or in any case predominantly in the axial direction. At the same time the stiffening element forms an element that restores the bending movement and has a higher flexural rigidity than the bending element. The bending element is coupled to the control element, which exhibits an axial movement that controls the corresponding bending movement of the distal portion, or forms a part of the control element.
The stiffening element and the bending element can be introduced in each case as an independent element or rather component into the respective axial subregion of the distal portion or can be formed integrally as a part of a solid material of the distal portion and can be designed in an optimally adaptable way for its functions relating to restoring the stiffness and/or actively generating the bending movement, so that there is no need to design any other material of the catheter instrument in this region—typically a solid material, provided with one or more lumens, or a coaxial tube unit—to fulfill these functions. As a result, this feature makes it possible, if desired, to use, for example, a very pliable solid material for the basic structure of the distal catheter portion that does not have to act in either a stiffening or flexion determining manner. Rather the restoring rigidity is guaranteed by the stiffening element that is incorporated, for example, as a separate element into the pliable solid material or is formed by a solid material zone that exhibits a higher flexural rigidity. The bending element defines together with the control element the active bending movement. The bending element can enable in interaction with the stiffening element an enhanced functionality in terms of the active bending movement as compared, for example, to the conventional bending arrangements with a tension wire control element that acts only on a distal end cap region of a homogenous solid material of the distal portion.
In a further development of the invention the stiffening element extends from the distal portion into the shaft portion. In this way the stiffening element can contribute to providing the shaft portion with a flexural rigidity that is typically necessary for the shaft portion and that is significantly higher than the flexural rigidity of the actively flexible distal portion.
In a further development of the invention the control element is formed by a tension wire that is guided through a hollow channel of the bending element and is coupled to a distal end region of the bending element by means of, for example, a thickened head piece. A tension wire that is suitable for the present invention includes any type of wire that is used in the customary way for this purpose. For the sake of simplicity the term tension wire in the present invention shall also include tension cables of any kind.
In an additional embodiment the bending element has two hollow channels, through which the tension wire is guided in one piece so as to form a return bend at the distal end region of the bending element. This simple design feature makes it possible to produce the bending movement by a synchronous pulling at the two proximal sections of the tension wire, so that the return bend transmits the pulling force to the bending element.
In a further development of the invention the bending element is implemented by an elastically compressible helical spring element or hollow rod element or an elastically compressible solid material zone of the distal portion. In the specific case the bending element can be formed, for example, by a helical spring having windings, which are axially spaced apart from each other in the unstressed state, or by a relatively flexurally pliable solid material zone of the distal portion.
In a further development of the invention the stiffening element is formed by an elastically tensible helical spring element or rod element or an elastically tensible solid material zone of the distal portion. In the specific case the stiffening element can be formed, for example, by a helical spring having windings, which are axially spaced apart from each other in the unstressed state, or a relatively flexurally pliable solid material zone of the distal portion.
In a further development of the invention the stiffening element and the bending element can be arranged opposite each other relative to a longitudinally central axis of the distal portion. This feature allows at least one bending movement in the plane of the stiffening element and the bending element in the one and/or the other bending direction, depending on whether the bending element is subject to a push or pull force by means of the control element.
In a further development of the invention the bending assembly comprises at least two bending elements, which are arranged opposite each other in the plane of the bending movement, and at least two stiffening elements, which are arranged side by side in a plane transversely to the plane of the bending movement. This feature allows the distal portion to be bent in both directions in the plane of the bending movement, even if only control elements, which work by means of pull forces and not by means of push forces, are used exclusively.
In a further development of the invention the distal portion of the catheter is made of a solid material or consists of two coaxial tubular elements. In this case the bending assembly is provided in the solid material or in the annular space between the coaxial tubular elements. If the bending element and the stiffening element are designed as independent elements, which satisfy the stiffening function and/or the bending actuator function, then the solid material and/or the coaxial tubular elements do not have to be designed to fulfill these functions. They need only be selected in such a way that they do not inhibit these functions of the bending element and the stiffening element. As an alternative, the bending element and/or the stiffening element can be formed by a corresponding zone of solid material, which in this case is constructed of a plurality of materials in the form of multiple zones.
In a further development of the invention the distal portion of the catheter has a central axial working channel and/or one or more off-centered axial working channels. The working channel(s) can be used, for example, for the customary catheter functions, such as for conveying a fluid or gas or for operating a functional element that is needed on the distal end, like a mirror, a knife, scissors, a sensor, etc. For this purpose the respective working channel can also extend preferably in a continuous manner through the shaft portion.
In the design of this aspect the distal portion is made of a solid material surrounding the central axial working channel with a non-uniform thickness. In this case a correspondingly flexurally rigid solid material zone, which lies in a region in which the solid material has negligible thickness, acts as the stiffening element. In addition, the tubular solid material can be easily manufactured, for example, by an extrusion process using at least two materials of different flexural rigidity. In an additional design the solid material also has a zone that acts as a bending element and that lies in a region of greater thickness. Even for this design the solid material can be fabricated, for example, as a suitably extruded tubular component.
In a further development of the invention the catheter instrument comprises a plurality of bending assemblies, each of which has at least one stiffening element and at least one bending element of the aforementioned type. In this case the bending assemblies are provided in different axial subregions of the distal portion; and at least two bending assemblies have bending movement planes that do not extend parallel to each other. This feature allows the distal portion to be bent in a plurality of non-parallel planes of the bending movement.
In a further development of the invention the distal portion of the catheter comprises at least one light guide element and, coupled thereto, a luminous ring. In this case the light guide element is accommodated in an axially extending manner in a working channel of the distal portion. At the same time the luminous ring can serve as a light guide on the distal front end of the catheter.
In a further development of the invention the distal portion of the catheter comprises a distal end piece, which can be moved in an axially elastic manner. This distal end piece is connected to at least one guide pin, which can be guided in an axial hollow channel of the distal portion in such a way that it can be moved in an axially elastic manner. In this structurally simple way the distal portion of the catheter is flexible in an axial elastic manner on its distal end, so that the risk of injuring, for example, a body tissue in the course of inserting the catheter instrument can be eliminated.